The ultimate objective of this work is the elucidation of the details of molecular interactions of biological macromolecules (proteins and nucleic acids) in solution with each other and with small effector molecules, such as hormones and drugs. Generally such interactions are mediated by conformational alterations in the macromolecule. The method of choice to investigate the conformations of proteins and nucleic acids in solution is nuclear magnetic resonance (NMR) spectroscopy. We have used 1H, 2H, 13C and 31P NMR in combination with selective stable isotopic enrichment (2H and 13C) to study the conformations and solution properties of proteins and DNA. Currently we are focusing on the effects of base sequence on the conformational transitions of polydeoynucleotides and the effects of cytotoxic drugs on those transitions.